Environmental Engineering Reference
In-Depth Information
with its own pros and cons. Methanogenic digestion is socially and environ-
mentally beneficial waste treatment process; however, the unit cost for methane
production needs to be lowered. Ethanol production from corn yields marginal
energy return; the environmental consequences of all crop-based ethanol
require consideration.
An MFC is a developing renewable energy technology that has a unique
niche with respect to other microbiological processes. Instead of generating
biofuels, an MFC generates electricity directly from organic material, including
wastes. An MFC exploits the unique respiratory activity of ARB that oxidize
organic fuels and transfer the electrons released from oxidation to the anode.
Much like in anaerobic digestion, a community of microorganisms that includes
fermenters and ARB appears to cooperatively channel electrons from organic
fuels to the anode. The interaction between two groups of organisms is an
exciting area of research for environmental biology and microbial ecology.
The current generation from an MFC is determined by the reactor pH,
the presence of competing sinks for electrons, mass transport of electron
donor, and electron-electron conduction in the biofilm. A mass balance on
COD is a useful tool for establishing performance criteria, and we define the
important and unique criteria of OE, PE, RCE, CCE, ECE, PEE and FoSaC.
MFC developers can use these performance criteria to track different facets of
MFC performance, thereby identifying bottlenecks and opportunities for
improvement.
References
1. Goldemberg, J. and T.B. Johansson (2004). World energy assessment overview: 2004
update. United Nations Development Programme, New York.
2. Hall, D.O. and F. Rosillo-Calle (1998). In Survey of Energy Resources, 18
th
Edn. World
Energy Council, London, 227-241.
3. Chynoweth, D.P., J.M. Owens, and R. Legrand (2001). Renewable methane from anae-
robic digestion of biomass. Renew Energ 22, 1-8.
4. Energy Information Administration (2005). Annual energy outlook: with projection to
2030. U.S. Department of Energy, Washington, DC.
5. U.S. Environmental Protection Agency (2006). Municipal Solid Waste Generation, Recy-
cling, and Disposal in the United States: Facts and Figures for 2006. U.S. Environmental
Protection Agency, Washington, DC.
6. Borjesson, P. and M. Berglund (2006). Environmental systems analysis of biogas systems -
Part 1: fuel-cycle emissions. Biomass Bioeng 30, 469-485.
7. Xiao, J.H. and J.M. VanBriesen (2006). Expanded thermodynamic model for microbial
true yield prediction. Biotechnol Bioeng 93, 110-121.
8. Wyman, C.E., B.E. Dale, R.T. Elander, M. Holtzapple, M.R. Ladisch, and Y.Y. Lee
(2005). Coordinated development of leading biomass pretreatment technologies. Biores
Technol 96, 1959-1966.
9. Angenent, L.T., K. Karim, M.H. Al-Dahhan, and R. Domiguez-Espinosa (2004). Produc-
tion of bioenergy and biochemicals from industrial and agricultural wastewater. Trends
Biotechnol 22, 477-485.